MARIA MARGARETTE COLUMNA STEM II ZARA 1. WHAT HAPPENS DURING PRE-EMBRYONIC AND EMBRYONIC DEVELOPMENT? The pre-embryonic period, known as the germinal phase, is the first and shortest phase embryonic development. It last from fertilization to the second week of to the second week of the embryo’s life. In this phase of embryo development, the zygote repeatedly self-replicates. Starting in the second week after fertilization, the embryo starts to develop distinct cell layers, form the nervous system, make blood cells, and form many organs. 2. WHAT ARE THE MAJOR EVENTS DURING FERTILIZATION? Sperm preparation Sperm- egg recognition Binding Fusion of sperm and pro-nuclei and activation of zygote 3. HOW DOES THE DEVELOPMENT OF THE GENITALS DIFFER IN MALES AND FEMALES? Both sexes develop urogenital and anal membranes early in sexual differentiation. Under the influence of androgens ,mostly DHT, the male tissues will enlarge and fuse to create the penis and the scrotum. In comparison, the female tissues will develop into the female genitals in the absence of androgens. Male genitals development. Scrotum and testes grow larger Penis becomes longer and seminal vesicles and prostate gland grow Hair begins to grow in the public area and later on the face and underarms Ejaculation becomes possible(usually in mid adolescene around 12-14 years old) Female genitals development Hair begins to grow in the public area and later on the underarms Maturation of the breast ,ovaries, uterus, and vagina Start of menstruation